Use of a Soluble Glass Bolus to Provide a Supplement of Copper and Selenium for Grazing Cows

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  • 水溶性ガラス投与による放牧牛への銅とセレンの補給
  • スイヨウセイ ガラス トウヨ ニ ヨル ホウボク ウシ エ ノ ドウ ト セレ

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Abstract

A soluble glass bolus containing copper (Cu) and selenium (Se) was orally administered to nonlactating and nonpregnant cows. Fourteen Japanese Black cows were divided into 2 groups 2 months after the opening of grazing. Each of 7 cows in the first group received a glass bolus and the other 7 cows were untreated. Copper content in forages, ranging from 5.5 to 8.2mg/kg dry matter, suggests that Cu may be marginal, and that Cu is preferably supplied to cows during the grazing period in these pastures. Selenium content in almost all forages was below 50μg/kg dry matter. These values were much lower than the dietary requirements of Se for cattle, indicating that Se must be supplied to the cows grazing in these pastures. Plasma Cu concentrations were increased by the bolus administration and the plasma Cu concentrations were significantly (p<0.01) higher in the bolus-administered cows than in the controls for 3 months after administration. The difference in plasma Cu became insignificant thereafter. The change of plasma ceruloplasmin activity was similar to that of plasma Cu level in the bolus-administered cows. Compared to the beginning of the experiment, blood Se levels were decreased during the grazing period in both groups but the reduction was larger in the controls. Consequently, blood Se concentrations were significantly (p<0.05) higher in the bolus-administered cows than in the controls 2 months after administration. Blood Se concentrations did not differ between the administered and control groups thereafter. Three and four months after the administration, blood Se levels in every administered cow were higher than 20μg/l which was thought to be the lowest limit of normal Se level though 2 of the control cows showed blood Se levels below this limit. Plasma creatine phosphokinase activity was not different between the administered cows and controls throughout the experimental period. It is suggested that the efficacy of the supplementation of these minerals lasts 3 months. It is conceivable that the administration of a glass bolus is one of the ways to supply Cu and Se to grazing cattle.

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